Polycarbonate resin has excellent toughness, impact resistance, thermal stability, self-extinguishing property, dimensional stability, and heat resistance, and accordingly has been widely used in the production of electro-electronic products such as mobile phone housings, backlight frames, connectors, and the like. Polycarbonate resins have also been used to produce automobile parts such as head lamps, instrument panels, and as a substitute for glass or similar materials in lens and other applications requiring transparency and impact resistance.
However, when a product requiring transparency is made of polycarbonate, it can exhibit deteriorated or reduced scratch resistance as compared to glass. Polycarbonate materials can also yellow over time upon exposure to sunlight.
Polymethylmethacrylate (PMMA) resin has excellent weather resistance and transparency, and excellent adherence and strength such as flexural strength and flexural strain which is different from polycarbonate resin. Accordingly, PMMA resins can be used in applications such as adhesives, lighting materials, and building materials. However, PMMA has inferior impact strength as compared to that of other thermoplastic resins, so its use is limited in thin products having a certain thickness requiring sufficient impact strength.
Accordingly, when a transparent polycarbonate resin having excellent toughness and a transparent PMMA resin having excellent scratch characteristic are alloyed, it is expected that the alloy would provide both excellent impact resistance and excellent scratch resistance.
However, as mentioned in Japanese Patent Laid-Open Publication No. 1994-128475, when polycarbonate resin is alloyed with a PMMA resin, the molecular weights and weight ratio are limited to a certain range due to the miscibility and refractive index differences between the two resins. When the molecular weight and weight ratio levels of the polycarbonate and PMMA are outside of certain ranges, there is a concern that the product will exhibit a pearl effect, uneven color, and opaqueness.
Accordingly, much research has focused on improving the scratch resistance of polycarbonate.
For example, U.S. Pat. No. 4,027,073 discloses a surface treatment method of using a Si compound and a method of improving the scratch characteristic through acrylic UV coating. In addition, U.S. Pat. No. 5,338,798 discloses a method of using syndiotactic PMMA; U.S. Pat. No. 5,292,809 discloses a method of using a fluorine-substituted bisphenol; and U.S. Pat. No. 4,743,654 discloses single-phase blends of polycarbonate resin and polyalkylmethacrylate. However, the compounds have problems such as high cost and limited application fields.